


The Screepy Crawlies

by Nillas NSFW Corner (Agraulis_vanillae)



Category: Undertale (Video Game)
Genre: Anal Sex, Blow Jobs With Teeth, Challenge Response, Cocoon, F/M, Gender-Neutral Pronouns, Goopster, Goopster probably used it, Heavy Petting, If there's a hole, M/M, Questionable Anatomy, Restraints, Screepy Challenge, Screepy- sexy and creepy, Tentacles, Undertail, dubcon, oral sex?, questionable life choices, w.d. gaster - Freeform
Language: English
Status: Completed
Published: 2017-02-14
Updated: 2017-02-18
Packaged: 2018-09-24 07:01:56
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 3,595
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9709496
Author URL: https://archiveofourown.org/users/Agraulis_vanillae/pseuds/Nillas%20NSFW%20Corner
Summary: This is in response to the Screepy Valentine's Challenge by PancakeUniverse/PancakePants! https://agraulisvanillae.tumblr.com/post/155354176272/screepy-valentines-masterpostThis challenge includes first Gaster/Reader, and will be updated soon to include Muffet/Reader! The point is that the pairing is both sexy, and a little creepy, it can't be noncon but you do kind of wonder what you're doing, with both your partner and your life.





	1. Liquid Shadows

You were groggy when you awoke to the drop of temperature in your room. Nestling further in your bed, pulling blankets over your shoulder and curling up to keep warm, you almost missed the way the air moved unnaturally in the room. It alerted you to the sense of your space not quite being your own.

What was it? A cold wind?

…

No, it was more accurate to say it was more like a chilling breath. Your eyes opened, and you stared into the charcoal darkness, the contours and shadows of your room visible as your vision adjusted to the darkness. You sat up slowly, your blanket falling past your shoulders and gathering over your lap as you rested your hands in the residual warmth under the folded layers. Outside your bedroom window, the shadows of the tree branches stirred and wavered with a soft rustling, but there was something off about the shadows drifting across the floor of your room. 

Suspicious, you watched the leaves of the branches shift shape, with the edges of the shadows rounding out in shape and then thinning sharply again like the leaves were breathing. The fine hairs on the back of your neck stood straight up, goosebumps following the chill down your arms, and the presence curling around your arms while a completely separate sensation wraps across the contour of your exposed ankle. You move your leg back underneath the blanket, reaching to rub off the cold feeling underneath your pajamas, still too foggy from sleep to feel anything more than mild discomfort. The sensation follows your leg up, tracing the contour of your calf, wrapping across the knee, only for the sensation to stop and press at your inner thigh. You paused, suddenly afraid to reach down any further and touch what may lurk under your sheets.

That's when the shadows contorted around you, shifting to engulf both of your arms in an airy wind. The touch deceptively light, but firm as you try to pull free, startling you fully awake with the unexpected weight of it keeping you in place.

You make no mistake now, this was no wind, nor was it shadow. However, you could not make sense of where the creeping feeling advancing to your other leg was coming from, and you pulled it back before it could bind you. A mistake, the other shadowy sensation moved forward and caressed up the length of your groin, producing a gasp from you. The lightness of the touch produced a warmth throughout your body that conflicted with the cold sensation, but you had no time to focus on it as a light flickered before you, making you freeze in shock.

The misty light formed a pale face, flickering like television static before pulling itself into existence, and you felt your face being cupped before all at once every touch settles into a heavy grasping liquid coiling across your body. The face drifted close, cracked white skull and a faint violet glow from deep within the drooping eye socket. The face took up your field of vision before the hand at your cheek drew a line from your cheekbone, and traced your jaw down to your chin, compelling you to allow your mouth to be taken into a shallow kiss.

And then you were being pulled up by your leg, past your blankets and up into open air. Slick liquid swelling around your shoulders pushed your back firmly from underneath your shirt, creeping down your spine to raise your hips and support the otherwise awkward position. You were suspended, liquid seeping through your hair and chilling your head, neck, and scalp. Your arms were still weighed down, pulled into a V directly behind you, but you didn't dare look down to see how far up you'd been abducted from the warmth and safety of your bed. You could only guess at how high you were by the proximity of the ceiling, but it was coated in flowing liquid, dripping down onto you, staining your clothes, and merging back with itself. 

Uncertainty had your heart pounding, your skin felt cold, but you could feel your blood heat up with your sensitivity rising. You were defenseless against what happened next, but it was hard to question what the anticipation was doing to you. 

For a minute, it seemed like the entity was creeping along itself, pulling itself above you again. The face hovered above you watchfully. You cringed as the liquid continued to spread through your shirt and pull it over your stomach, ribs, and over your chest with the added weight. Your shorts were slick and heavy across your thighs too, as if you'd wet yourself, but the material was somehow traveling up against the flow of gravity to expose you completely. Underneath it, the swell and pulse of liquid shadow dripped off your thighs laid bare to the air of the room, leaving a viscous residue that made your thighs slide when you pulled your free leg close to your stomach. You squirmed, rubbing your thighs together before the addition of white skeletal hands appearing signed something foreign.

A very solid hand caressed your groin, gripping your ass, and then another hand seemed to appear from nowhere to spread you out. Despite the way the muscles in your thighs twitched appreciatively to the treatment, you weren't at all sure what to think of being laid out like that. You felt obligated to speak up, “Uhhh... g-gently if you're gonna go that route...” 

The room was silent, but for the sound of liquid slithering through the ceiling, shadows converted into solid matter and gathering above you.

Then alarmingly, the pool began pouring down, coating your nether regions in chilling fluid. Shivering, you weren't sure what to expect other than feeling like you'd been doused with cold water until it was entering you in dribbles, first dripping into your ass and then snaking throughout your groin. You arched back with no small measure of discomfort as you were slowly filled, and you groaned, “Uh-ugh, fucking hell-”

The skull leaned forward to kiss you again, fluid dripped down disconcertingly from their open mouth and filled your mouth, wrapping along your tongue as you shook your head and attempted to keep your throat closed to the intrusion. The taste of star anise permeated your mouth and nose powerfully, overwhelming your sense of smell. You were very nearly distracted from the way the fluid inside your ass and entrance had ceased its liquid movement inside, settling like jelly, and seemed to pulse, expanding with each twitch.

Within seconds you were suddenly very full and much deeper than you'd ever imagined anything reaching. The fluid in your mouth became solid as well, more like a proper muscle and less like you might drown at any moment, and stroking along the underside of your tongue, dextrously writhing. Their teeth parted from your lips, saliva and goo strung from your mouth to their tongue exiting. Everything went still for a few moments, with you staring into this white broken face, and eventually it occurred to you that this strange entity was waiting. What could you do though, when you were suspended in midair with your arms bound beneath you?

You wiggled from your shoulders, and then your abdominal muscles, pausing as you felt fluid dribbling out of you with the slight rocking motion. You couldn't decide whether to be disgusted or turned on, and decided very pointedly to ignore the copious amounts of slime that was apparently being emitted inside you. You stretched your legs to discover that you were close enough to the slime soaked ceiling to press your heel to it for leverage. The solidified matter began sliding out, no longer cool but heated from inside your core.

Then you slipped unexpectedly, the slime making the ceiling too slick to support your weight right, and fell back into it with an audible 'squelch!' and a yelp as you were thoroughly impaled. Something was dripping out, you or them? You had no idea what was formed, but you felt like there was more inside than you'd ever taken before before, every muscle inside you contoured to the penetrating substance. Was this their dick? You were more than a little foggy on the matter, but it had some yield as you squeezed around. More so, canting your hips forward or backward, you could feel yourself being breached deeply no matter what. You braced your heels against the ceiling again, sliding as far off as you could without sliding abruptly like before, and then dipped your hips down to drive the entity into you once more.

Disembodied hands grasped at your waist and pulled you up, before slamming you back down, and you cried out only for their long tentacle to be shoved into your mouth again. There was no more balancing with the ceiling, your legs suddenly squeezed and pulled apart. There was no friction, simply more and more fluid dripping out of you with each ensuing thrust. Whimpers and gasps spilled out of your mouth along with saliva tinged with black. Losing yourself to the intensity of each a sliding stroke, you closed your eyes to the face, all too aware how much it looked like you were fucking Death and tried your best to thrust your hips forward. 

It was throbbing between your legs, more and more, expanding with each thrust. The hands pressing down at your waist dug painfully, squeezing harshly at the crest of your hips, and forcing further in greedily. Each extra inch was cold in stark contrast to what you've accepted inside of you, and threatened to give under the strength of your rhythmically clenching muscles. If you had more room in your mind for anything more than the pain-pleasure radiating deep inside your core every time they bottomed out inside, you'd be concerned that something might break off inside you. 

You clenched your hands, trying to grasp as if to keep you anchored, but you were still bound tightly. The tentacle grasped around your tongue, writhing and thrusting into your throat with ever present urgency and you mewled desperately, needing to come up for more air or elevate your head. A fluttery almost panicky feeling gripped your chest, accompanying the buzzing lightheaded sensation as even more black liquid-yet-not-liquid was thrust inside, and warm fluid gushed out to coat your ass and thighs. You can feel yourself falling under, trance-like as your orgasm snapped through you hard, vision going white and thrusting your hips into them with fervor. The long kiss ended abruptly.

The disembodied hands ground your hips down hard, your eyes flying open to see the silent snarl contorted on their face before a hard stream of hot cum coated inside of you.

And then without any warning, the solid mass supporting you dissolved and you fell, liquid pouring along with you. A sense of vertigo overwhelmed you, before you hit the bed hard, bouncing disconcertingly before you came to a rest onto soaked sheets.

Dizzy and disoriented from the head-rush for a few moments, your shoulders sore as hell from the awkward position, you lay there for a few minutes with your body cooling rapidly in evaporating black liquid. You stared up at the ceiling, still dripping and yet no longer pooling and writhing. The shadows of your room were once again still, only the shadow tree branches softly drifting in the light of your window, not quite dark anymore though you were reluctant to describe it as light.

When you moved, fluid squirted out of your ass and your groin. You realized your shirt was still pushed up, your pajama pants pulled down lewdly around your knees, and that not only were you drenched but all of your sheets on your bed was soggy too.

You grimaced. Whoever that was, they left you in one hell of a wet spot.


	2. It's a Reflex

**Summary for the Chapter:**

> You get it on with Muffet. It's not quite the same as getting it on with Spiderman.

You went to her bakery every morning before work. Coffee and donuts dipped in spider cider likely wasn't what your doctor ordered for half of her meals every day, but you weren't about to sacrifice sleep to actually cook something. Besides, what you were willing to sacrifice sleep for was a little time to flirt with the cute spider monster in charge of the bakery. Morning after morning, you'd sit at one of the tables near the serving counter, just to drop line after line on her.

 

At first, Muffet ignored you. However, given the way she's dispatched human customers that nearly crushed spider workers, you felt like this was no barrier. After all, you weren't the one that got suspended in a cocoon and unceremoniously dumped outside the cafe, or forced to entertain the 'pet'. In fact, you'd gotten quite used to the not-so-little fellow, letting the strange cupcake-spider hybrid nibble at the donut crumbs on your hands with the oddly precise movements of its mandibles.

 

Eventually, she acquiesced to your charms, and began flirting back. Flirting successful, you'd gotten bolder, running your hand over her thigh- or what passed for her thighs at any rate- and thereby leading you to your current predicament.

 

“So dearie, what do you enjoy?”

 

Your back to the bed, hair lightly gripped, hands running up and down your sides before sliding under your shirt. Another hand was at your crotch, rubbing slowly so that you rocked back and forth into her touch. You had licked her mouth for entrance before oh so cautiously navigating your tongue past her fangs. It wasn't long before she had pushed you back and her tongue was in your mouth, and you let her take the lead like that before she'd separated to ask you that.

 

You considered your answer very carefully. You could feel your body thrumming, pulsing in anticipation for what's to come, but you knew from observation that she was a predatory monster. She might mistake 'being eaten' for being devoured and vore certainly wasn't on your list of kinks.

 

“I'd really like to use my mouth for something a little different,” you took a moment to curl your tongue and lick her bottom lip again. “But I also... want to be pleasured in a way that I have absolutely no control over it, please.”

 

“You ask so prettily for it, don't you?” Muffet leaned down into another sloppy kiss, fangs nearly catching into the softness of your mouth again. “Let me make sure you're secured.”

 

You weren't totally sure what she meant, as she didn't move away to get rope, or handcuffs, or even a blindfold. A few heartbeats later, you leaned up for another kiss, feeling one hand leave from between your legs. Then next thing you knew, she'd pulled up some sort of sticky silk-like thread. She'd grabbed your hand and pulled it up, kissing the inside of your wrist and rubbing her fangs against it, and then wrapping your hand in sticky thread. She started climbing up the ceiling, much to your disconcertion, to attach the strand so that your hand was pulled up. In the process, you could see the silk being produced from her spinneret. It was a set of four slightly curled hooks that acted almost as extra appendages, dexterously gripping the silk and drawing it out.

 

She crawled back down the wall, using her thread for leverage. As her delicate hands scaled the silk with ease, the thread bobbing back and forth hypnotically with each touch somehow pulling free from the strands that stuck so tightly to your skin, you wondered oh so briefly if you weren't a little out of your depth. However, there was one thought that tugged at your mind that couldn't stop you from getting right back into it.

 

She nearly climbed down when you tugged on the silk, causing her to pause in her movements and hang suspended as you sit up, your face close to hers, “H-hey hold up real quick! Kiss me upside down like that scene from Spiderman!”

 

Her eyes blinked one at a time as she processed your request, and then reached down to caress your chin. “Ahuhuhu. Tell you what, dearie, I'll kiss you like this if you'll do a little something for me.”

 

She leaned further down, her mouth nearly brushing yours when she whispered, “I've seen the way you've stared at my spinnerets. So I'll kiss you here, and I'll kiss you again...” She tapped your chest. “... and again... and again. In return, I'd like a long wet kiss of my own.”

 

One of her hands reached down, past where you would've thought her pussy would be, and tapped at the back of her thorax. With an extreme jump in your heart rate you hadn't thought was possible, you nodded. Maybe it was just nerves but you might be more than a little unprepared for that particular request. However, her eyes lit up and she pulled your head up for another long breathless kiss, and you could've sworn you forgot why you had any reservations at all.

 

“You. Are. Such. A delicious little love.” She kissed the pulse on your neck, planting more smooches down to your clavicle and all the way down your chest. As her body moved to press closer to your head, you did your best to reciprocate, using your web restraints to kiss down her lithe body, slender and graceful in form like a dancers except for the wide thorax that gave her such a luscious hourglass figure even in clothes. Soon enough- not too soon, and yet much much too soon, you were face to rear of those hook-like spinnerets.

 

Muffet's mouth was latched onto you between your legs like there was no tomorrow, and the intense pleasure was running through you with toe-curling pulses. Yet... you weren't quite sure how to navigate this particular anatomy. With a tentative lick, you were hoping to find that the hooks would be... fleshy maybe? Sensitive? But no, this was most definitely the hardened chitinous shell much like the plates around her stomach that fascinated you so when you were stripping her blouse off her, and down to the bloomers. Which meant you were going to be much more thorough in your explorations.

 

“Don't be shy, I don't sting~” Muffet encouraged breathlessly, with just a little singsong mixed in with a growing impatience in her voice. Time to nut up or shut up, and you probably would have to if you were going to 'nut' at all.

 

Leaning up again, you pressed your thumbs to the spinnerets in an attempt to spread them out, hearing a hiss down lower you readjusted your grip. Tenderly then and not too widely, and feeling her limbs relax around you, you pressed your mouth into the gap. It was different to press your tongue against the inside of a spider's thorax, indescribable in that she definitely didn't taste like anything you'd describe as human. Maybe a hint of... citrus, though it wasn't quite the same taste, it was the closest comparison you could think of. Her flesh offered some resistance before your tongue could penetrate, much softer and Muffet's body shivered as you suddenly slipped inside.

 

“Mm yeah, just like that...” she bore down on you and you were forced to all but unhinge your jaw to accompany the width of her thorax. Your tongue was being sucked in, and you did your best to move around the extreme suction. Welp, you're pretty sure there wasn't anything in the world that could prepare you for this conundrum.

 

Meanwhile, Muffet had almost stopped blowing you completely, gasping around and whimpering with delight. You got the idea that maybe if you managed to curl your tongue just right, you could finish her off and move on...

 

“Nngh that's right, take it... take me so good~” Muffet demanded from your crotch.

 

…but it seemed that no matter how she rocked into your mouth, you simply weren't able to push her over the edge. Not to mention, there was some questionably hard bits the further you went, and something sticking to your tongue in such a way you had trouble not imagining exactly what it was. You couldn't use your hands at all to help you work her along, which was really starting to work against you, especially as she got a little sloppier and you felt fangs brushing against you with her tongue.

 

To make matters even more worrisome, she was lifting her spinnerets from your mouth, you could feel them moving of their own accord before your mouth parted from them and to your open disbelief, she began weaving a cocoon all around you, strand laying over strand of thread wrapping in a T around your sternum and down your chest. She continued weaving, seemingly unaware of her actions before your chest was thoroughly encased.

 

“Um, Muffet? I'm uh- kinda covered now.” You mentioned hesitantly, and she stopped what she was doing to look back.

 

“Oh!” She sat up, thorax in your face briefly before she turned to apologize. “I just seem to... it's a reflex.”

 

You felt like an asshole now, for getting so creeped out, but you really weren't used to 'handmade' rope being utilized at random. Especially when the weaving had been working its way up to your neck next, and you're pretty sure you needed to breathe. You admittedly sheepishly, “I mean, it's not comfortable. But things happen right? Can you just help get some of this thread off of me?”

 

“Dearie, what do you mean?” She asked, genuinely puzzled.

 

 

**Notes for the Chapter:**

> I apparently can't help my sense of humor, so maybe not so heavy on the smut in this last chapter. If anything, I'd probably rate this Mature rather than Explicit, but oh well. I hope you guys enjoyed, and (late) happy Valentine's day once more!

**Author's Note:**

> Alternative titles include:  
> "Hey can you not wake me up in the middle on night for sex, I have to work tomorrow",  
> "Why Goop Sex isn't Sexy", and very direct and to the point, "The Wet Spot". I don't know why I have to work at NOT parodying the things I write. If you feel the need to talk to me, feel free to comment or talk to me using my tumblr! Good luck with your Valentine's misadventures, stay safe, and have fun!  
> https://agraulisvanillae.tumblr.com/


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